North Korea recently jammed GPS signals in South Korea in an apparent bid to disrupt Seoul's annual military drills with U.S. forces, government sources said Sunday.

GPS signals in Seoul and nearby cities, including Incheon and Paju, were temporarily disrupted on Friday afternoon, causing mobile phones and certain military equipment in the area to malfunction, the sources said.

"My understanding is that errors were detected in a very few equipment within the telecom industry," a defense official said. "Some measurement equipment in artillery units was also affected but only very slightly."

The jamming signals are thought to have come from vehicle-mountable devices at military units north of the inter-Korean border. Former Defense Minister Kim Tae-young said in October that he had intelligence that the communist regime had imported from Russia such devices capable of jamming GPS signals.

"The jamming signals came sporadically every five to 10 minutes," an intelligence official said, adding that North Korea was likely testing its imported devices.

Defense and intelligence officials said they suspect the jamming was aimed at disrupting the annual Key Resolve military drills between South Korean and U.S. forces, which started four days before the malfunctioning incident.

It also came nearly a week after North Korean representatives at the inter-Korean border village of Panmunjom repeated their threat against the drills, saying their armed forces would launch "an all-out war of unprecedented scale" and turn Seoul into "a sea of fire" if provoked. (Yonhap)